1. Field of Invention
The present invention relates generally to the field of spectral imaging. More specifically, the present invention is related to a method and apparatus for real time recognition and displaying of diseased tissue such as cancerous and pre-cancerous lesions. A physical model of the present invention is included herein in Appendix A and is hereby incorporated by reference.
The following definitions may assist in the understanding of terminology used throughout the specification:
photopic--relating to or being vision in bright light with light-adapted eyes that are mediated by the cones of the retina; PA1 luminescence--low temperature emission of light (as by a chemical or physiological process); also, light produced by luminescence; PA1 fluorescence--luminescence that is caused by the absorption of radiation at one wavelength followed by nearly immediate reradiation usually at a different wavelength and that ceases almost immediately when the incident radiation stops; PA1 phosphorescence--luminescence that is caused by the absorption of radiation at one wavelength followed by delayed reradiation at a different wavelength and that continues for a noticeable time after the incident radiation stops; PA1 halide--a binary compound of a halogen with a more electropositive element or radical metal halide; PA1 dysplasia--abnormal growth or development (as of organs or cells); PA1 neoplasia--the formation of tumors; PA1 endoscope--an instrument for visualizing the interior of the body; PA1 1) lesion feature location on the color image A using a multi-spectral array S in a logical combination operation (A.orgate.S); PA1 2) forming a gray level array difference C--B between the maximal B and minimal C contrast filter image array outputs and updating the maximal contrast image array B=(C--B); PA1 3) computing an accumulated histogram H(B) as an adaptive threshold function of the maximal contrast array B of the fractional number of picture elements (pixels) of grey level values encountered in a predetermined grey level range; PA1 (4) updating the multi-spectral array S by (a) forming a Boolean coded array E over array B using the function ##EQU1##
Halogens--fluorine, chlorine, bromine, iodine and astatine. Each member has a valence of -1 and combines with metals to form halides, as well as metals and nonmetals to form complex ions.
2. Discussion of Prior Art
Techniques for early screening, detection and diagnosis of pre-cancerous and cancerous tissues have been primarily limited to removal and testing of suspect tissue samples. Samples are typically tested in remotely located laboratory facilities using various known chemical and imaging techniques. Prior art methods lack accuracy and further fail to provide for real time screening and analysis.
One known prior art method of screening uses fluorescence emitted from the diseased tissues. Fluorescence has long been known as a tool used to detect cancerous tissue. Typically a tissue sample is removed from the body, injected with a spectrally responsive medium which in turn is selectively absorbed by the cancerous sections of the tissue sample. Once absorbed, a light source is used to illuminate the spectrally responsive medium and with cameras detect fluorescence. Other methods, without an injected liquid, use a laser of a shorter wavelength than fluorescence produced to excite the tissue. Sophisticated cameras are then used to detect the fluorescence. Examples of known prior art describing such methods are: U.S. Pat. Nos. 4,741,043; 4,965,725; 5,008,185; 5,093,866; 5,741,648; 5,507,287; 5,769,792 and 5,733,721 and articles "Multicolor Imaging and Contrast Enhancement in Cancer-tumor Localization Using Laser-induced Fluorescence in Hematoporphyrin-derivative-bearing Tissue"; "Laser Induced Fluorescence Spectroscopy from Native Cancerous and Normal Tissue"; "Fluorescence Spectra from Cancerous and Normal Human Breast and Lung Tissues"; "Use of a Novel Spectral Bio-imaging System as an Imaging Oximeter in Intact Rat Brain"; "Digital Spectral Imaging for Histopathology and Cytopathology"; "Fluorescence Diagnosis of Genitourinary Cancer" and "Cervical Fluorescence of Normal Women". In the prior art, as exemplified by Sekiguchi, U.S. Pat. No. 4,821,117, "Endoscopic System for Producing Fluorescent as Visible Images", issued Apr. 11, 1989, there is disclosed an endoscopic system which simultaneously displays a visible radiation image and a fluorescent image of an internal organ an a same display unit to identify any lesioned tissues in an internal human or animal organ. Sekiguchi requires that fluorescent material be applied to the tissue, At this point, the tissue is alternately illuminated with visible radiation and excitation radiation (laser light). A camera is synchronized with the light or emission sources such that reflected visible light is electronically captured and stored in a first buffer while the fluorescent image is captured and stored in a second buffer. The fluorescent image in the second buffer is intensified to a predetermined level. Both images are then applied to one or more video read heads for concurrent display. It is noted that tissue when exposed to laser light at selected frequencies can fluoresce over a spectrum of wavelengths.
In Alfano, U.S. Pat. No. 5,042,494, "Method and Apparatus for Detecting Cancerous Tissue using Luminescence Excitation Spectra", issued Aug. 27, 1991, the disclosed method illuminates a target tissue with a laser or monochromatic light source varied over a predetermined range of frequencies. This causes the tissues to fluoresce. The returns are then sampled for intensity, luminescence, and excitation spectra and the wavelengths at which maximum values for these attributes occur are determined. Alfano next compares these values with their counterparts in either known benign or lesioned tissues to determine the carcinomatoid status of the target tissue.
In a similar vein, Palcic et al., U.S. Pat. No. 5,769,792, "Endoscopic Imaging System for Diseased Tissue", issued Jun. 23, 1998, illuminates a target tissue with laser light to induce fluorescence excitation and white light for color imaging. This arrangement is limited in that it relies also on the autofluorescence contrast between lesioned and benign tissues for detection. Additionally, Palcic requires a multiple camera and elaborate beam splitting optical system in order to obtain multiple images.
Two examples of cancers which are treatable by early and proper diagnosis are cervical and bladder cancer. Cervical cancer is the third most common type of cancer in women. Approximately 2% of all women will develop some form of cervical cancer. Paramount to survival is early detection and treatment In men 40-80 years of age, bladder cancer is the fourth most common type of cancer. More than 40,000 cases are detected annually in the US alone. As with cervical cancer, early detection is necessary for optimal treatment. Known techniques for early screening include pap smears and colposcopy (with and without acetic acid) for cervical cancer and optically guided biopsy and cytology for bladder cancer.
Prior art methods fail to provide for real time screening and analysis critical to early and effective diagnosis. They also suffer from many drawbacks which make them impractical for use in the field such as the removal of a tissue sample from the body, eliminating any analysis in situ (at the place under inspection). Delays associated with typical laboratory analysis make it impossible to analyze the tissue in real time and create the possibility of laboratory errors such as contamination, lost or mixed-up results or a poorly trained staff's improper diagnosis. In addition, samples removed from the body are imaged at a microscopic level, typically a few microns, and therefore a determination of the extent, i.e. perimeter, of diseased tissue is not well represented Early malignant and pre-malignant and dysplastic lesions are often barely visible or even invisible under regular white-light video-scopes and are often missed by such prior art techniques. And finally, spectral analysis is limited to spatial analysis (pattern recognition) of the fluorescence.
Whatever the precise merits, features and advantages of the above cited references, none of them achieve or fulfills the purposes of the present invention. Accordingly, it is an object of the present invention to provide for a method and apparatus for real time recognition of diseased tissue.
It is another object of the present invention to provide for automatic detection of malignant and pre-malignant tissue by illumination of a target tissue with a light source whose characteristics concurrently enhance contrast between lesioned and benign tissue and facilitate removal of noise and other artifacts from resulting detected images without elaborate optical processing.
It is another object of the present invention to provide for a sharp image contrast between normal and malignant and pre-malignant tissues.
It is another object of the present invention to provide for a real time color image display of detected malignant and pre-malignant tissue on a regular video-scope.
It is another object of the present invention to provide for a method of "in situ" analysis of diseased tissue.
It is an additional object of the present invention to provide for "in vivo" recognition of diseased tissue.
It is an additional object of the present invention to include an analysis of diseased tissue using combined reflectance and autofluorescence.
It is an additional object of the present invention to combine multi-spectral and spatial (blob) segmentation and analysis.
It is an additional object of the present invention to be non-destructive of the target tissue and rely upon a macroscopic assessment rather than a microscopic evaluation of tissue samples or the like.
It is an additional object of the present invention to provide for a compact single camera architecture.
It is an additional object of the present invention to provide for a compact Metal Halide light source with special spectral characteristics with no need for special optical elements such as beam splitters, shutters, etc.
It is an additional object of the present invention to provide for a compact single camera architecture utilized for both color and diagnosing imaging.
It is an additional object of the present invention to provide for a system which enables visual detection discernable by technicians without highly specialized training
It is an additional object of the present invention to provide for multi-usage for all diagnostics and regular video-scope color imaging (e.g. colposcopy, cystoscopy and other endoscopic usages).
These and other objects are achieved by the detailed description that follows.